18 miles an hour may not seem terribly fast, but that's the new land record for legged machines. This speed was clocked by the Defense Advanced Research Projects Agency's (DARPA) robo-cheetah project, which is investigating technologies that allow machines to traverse terrain in new unique ways. Explains DARPA of this metal cat:

The "Cheetah" robot galloping at speeds of up to 18 miles per hour (mph), setting a new land speed record for legged robots. The previous record was 13.1 mph, set in 1989 [...] The current version of the Cheetah robot runs on a laboratory treadmill where it is powered by an off-board hydraulic pump, and uses a boom-like device to keep it running in the center of the treadmill. Testing of a free-running prototype is planned for later this year.

It's not clear why the Department of Defense needs a robotic cheetah, but would you really expect them to relinquish classified details of any real-life Voltron projects?